Electrophysiological effects of diltiazem in chronic bifascicular block

Abstract

Background: Literature on diltiazem in intraventricular conduction defects is meagre. We studied effects and safety of diltiazem in chronic bifascicular block using His-bundle electrocardiography and pacing. Methods: 23 patients with chronic bifascicular block were enrolled, all were in normal sinus rhythm. A baseline EP study,including, sinus cycle length (SCL), intra-atrial conduction time (PA), AV nodal conduction time (AH), intraventricular conduction time (HV), corrected sinus node recovery time (cSNRT), sinoatrial conduction time (SACT) and AV node wenchebach time, were assessed at baseline and repeated after diltiazem 0.25mg/kg followed by 0.0012mg/kg/min for 20 minutes. Results: Patients with normal sinus node function (N=21), showed significant prolongation of SCL (+18%, P=.001), cSNRT (+63% P=.002), SACT (+18%, P=.001), AH (sinus), AH (paced), and wenchebach point. Patient with sinus node disease (N=2) had greater prolongation of SCL (+52%), cSNRT (695 to 4260msec) and SACT (+140%). Both patients developed left atrial rhythm. HV interval, spontaneous (59 + 11msec to 60 + 12msec P=NS) and paced (59msec + 12 to 60 +12msec P=NS), QRS and QTc intervals did not change significantly. Conclusion: Diltiazem causes greater depression of SA and AV node in patients with sinus node dysfunction. Diltiazem did not affect the intraventricular conduction even in patients with prolonged baseline HV interval.

Keywords

• diltiazem
• chronic bifascicular block
• sinusnode
• Hispurkinje function